The present invention relates to a magnetic recording mode for improving surface recording density greatly and particularly to magnetic recording media, magnetic heads and a magnetic read-write apparatus using the same for achieving high-density magnetic recording.
Recently, improvement of recording density in the field of magnetic recording, particularly in magnetic recording disks, is remarkable and researches and developments are being hastened to achieve a higher-density read-write apparatus. The recording mode used in magnetic recording disks at present is a longitudinal magnetic recording mode in which recorded magnetization is directed to a track. In order to improve the recording density more greatly, a perpendicular magnetic recording mode free from self-demagnetization even in high linear recording density has been proposed or researched eagerly to be used in magnetic recording media (Iwasaki and Ouchi: IEEE Trans. Magn., MAG-14, 849 (1978), and so on) but the mode has been not yet put into practical use.
On the other hand, an obliquely magnetic recording mode free from self-demagnetization even in high linear recording density as well as the perpendicular magnetic recording mode is used in the field of VTRs in which longitudinal magnetic recording is mainly carried out. Particularly, as for a recording medium, an obliquely deposited Coxe2x80x94Ni tape has been put into practical use as a high-band 8 mm VTR magnetic tape, and a tape improved in characteristic is expected to be used also as a small-size digital VTR tape in the future (Yoshida, Shinohara and Odagiri: Journal of The Magnetics Society of Japan, Vol. 18, No. S1,439 (1994)).
In a magnetic recording using a ring type magnetic head used in magnetic recording at prevent, the fact that the obliquely magnetic recording mode is more preferable in high-density recording than the longitudinal magnetic recording mode and the perpendicular magnetic recording mode has been confirmed by the simulation by Tagawa et al in Tohoku University (Tagawa, Shimizu and Nakamura: Journal of The Magnetic Society of Japan, Vol. 15, No. S2,827 (1991)). Also in magnetic recording disks, it is expected that recording density will be improved remarkably by use of the obliquely magnetic recording mode.
In the case of a magnetic tape, a magnetic recording medium having an axis of-easy magnetization inclined to the recording direction can be formed by obliquely depositing, for example, a ferromagnetic Coxe2x80x94Ni alloy. In the case of a magnetic disk, it is theoretically possible to form a magnetic recording layer having an axis of easy magnetization inclined circumferentially on a circular substrate as disclosed also in JP-A-58-128023, but it is difficult to mass-produce such magnetic disks as products. Accordingly, to put magnetic recording disk devices using an obliquely magnetic recording mode into practical use has been considered to be almost impossible.
The present invention is intended to solve above-mentioned problems. A first object of the present invention is therefore to propose a magnetic recording mode for realizing an obliquely magnetic recording mode in a magnetic recording disk so as to provide a high-density large-capacity magnetic read-write apparatus which has been never provided. A second object of the present invention is to provide a magnetic recording medium suitable for realizing an obliquely magnetic recording mode. A third object of the present invention is to provide a magnetic head suitable for realizing an obliquely magnetic recording mode.
In order to apply an obliquely magnetic recording mode to a magnetic recording disk, conventionally, it was considered to make the axis of easy magnetization in a magnetic recording layer formed on a circular substrate inclined circumferentially. But, although it was possible theoretically, the process how to produce the magnetic recording medium was hard in terms of mass-production so that the magnetic recording medium could not be realized.
Therefore, the inventors of the present application have made researches actually upon the thought that obliquely magnetic recording can be carried out on a magnetic recording disk by using a magnetic recording medium having a radially inclined axis of easy magnetization of a magnetic recording layer formed on a circular substrate and by using a magnetic head for effectively generating a magnetic field radially. As a result, the present inventors have found that not only obliquely magnetic recording can be made but also extremely high recording density compared with the conventional longitudinal magnetic recording mode can be achieved.
That is, the above-mentioned first object of the present invention is achieved by performing recording, for example, by using a medium having an axis of easy magnetization inclined in the direction of the radius of a circular substrate and by using a ring type magnetic head having a yaw angle not smaller than 15 degrees. The second object is achieved, for example, by forming a medium structure in which the axis of easy magnetization is inclined in the direction of the radius of a circular substrate. The third object of the present invention is achieved, for example, by forming a structure in which a gap portion of a magnetic head is largely inclined with respect to the circumferential direction of a circular recording substrate to its radial direction.
Incidentally, in the process of researches for the present invention, the present inventors have found that read-write can be made sufficiently even in the case where a mode in which the axis of easy magnetization of a medium is projected in a direction perpendicular to the direction of relative movement between a magnetic head and the medium and the direction of head magnetic field is suitably inclined is applied to a magnetic recording tape, similarly to the case of the aforementioned magnetic recording disk. The present inventors further have found that, even in either case of a magnetic recording disk or a magnetic recording tape sufficiently high recording density can be achieved not only when the axis of easy magnetization of the medium is perpendicular to the direction of the relative movement between the magnetic head and the medium but also when the axis of easy magnetization of the medium is inclined suitably with respect to the direction of the relative movement between the magnetic head and the medium.
Further, the present inventors have applied a mode, in which a neutral period is provided without making inversion of the polarity of a recording current supplied to the recording magnetic head when the recording current is to be inverted, to the relative positional relation between the medium and the magnetic head. As a result, the present inventors have found that the output/medium noise (S/N) ratio can be improved greatly to the same degree as in the case of ordinary oblique magnetic recording so that the recording density can be improved.
FIG. 1 shows an example of the structure of a magnetic recording medium and a magnetic head for explaining a magnetic recording mode according to the present invention in which the axis of easy magnetization of the magnetic recording medium exists in a plane perpendicular to the recording track direction. The portion encircled with broken lines in FIG. 1 is a partially enlarged view to show an inclination relation between a recording track and magnetic poles.
First, the axis of easy magnetization 120 of a magnetic recording layer 110 of a magnetic recording medium 100 exists in a plane perpendicular to a recording track 130. Next, a gap portion 220 formed by two magnetic poles 210 and 211 of a magnetic head 200 is disposed to be largely inclined with respect to the recording track direction 130 so that an intensive magnetic field is generated in a direction which is inclined from the recording track direction. Accordingly, the magnetic field generated from the head 200 has effectively intensive magnetic field components also in the direction of the axis of easy magnetization 120 of the magnetic recording medium 100. In such a configuration as described above, magnetization of the medium in which the axis of easy magnetization 120 exists in a plane perpendicular to the recording track 130 is recorded by the intensive recording magnetic field components in a direction perpendicular to the recording track direction.
Because it has been found that, though it could not be thought of so far from the common sense, sufficient magnetic recording can be made even in the case where the axis of easy magnetization is perpendicular to the recording track, it is apparent that recording can be carried out in the case where the axis of easy magnetization of the medium projected onto a surface of the magnetic recording medium is inclined suitably with respect to the direction of recording track. Incidentally, though the reason is not apparent, it has become clear, from the result of the inventors"" researches, that the case where the axis of easy magnetization of the medium projected onto the surface of the magnetic recording medium is inclined suitably with respect to the direction of recording track is rather preferable in terms of high S/N and high-density recording than the case where the axis of easy magnetization of the medium projected onto the surface of the magnetic recording medium is coincident with the direction of recording track.
Incidentally, in the field of VTRs, for example, because of a helical scan mode, the direction of relative movement between the magnetic head and the magnetic recording medium is slightly different from the direction of the axis of easy magnetization of the medium projected onto the surface of the medium, while the direction of relative movement is substantially near to the direction of the axis of easy magnetization of the medium projected onto the surface of the medium. Further, in the field of VTRs, an azimuth recording mode, in which a relative gap angle (azimuth) between two heads used for recording and reproducing is inclined in advance by xc2x1xcex8 to reduce cross-talk by using azimuth loss, is employed in order to eliminate a guard band between tracks to thereby improve track density. If the axis of easy magnetization of the medium is projected onto the surface of the medium, however, the direction of projection exists at an angle near to the recording track direction. In contrast thereto, in the present invention, when the axis of easy magnetization of the medium is projected onto the surface of the medium, the direction of projection is inclined largely with respect to the direction of recording track. That is, the present invention is essentially different from the conventional case regardless of the direction of the gap of the magnetic head.